The purpose of this project is to develop the method for fast labeling proteins, peptides and oligonucleotides with fluroine-18 in high specific activity. [18F]-N-succinimidyl 4-(fluoromethyl) benzoate has been prepared from N-succinimidyl-4-[(4-nitrobenzenesulfonyl) oxymethyl] benzoate in one chemical step. Various reagents, solvents and substrates have been tested to find out the optimum reaction conditions. The best result was obtained when reaction was carried out in acetone at room temperature for 5 minutes using Kryptofix 2.2.2/18F-. Overall yields for the synthesis of [18F]-N-succinimidyl 4-(flurormethyl) benzoate were between 13% and 20% (EOA) in 45-50 minutes, including HPLC purification. The specific activity of 5000- 10000 Ci/mmol (EOB for [18F-N-succinimidyl 4(fluoromethyl) benzoate was obtained. The importance of this method is that the F-18 labeled ligand for labeling proteins can be made in one chemical step in high specific activity in a short period of time and the labeling process can be easily automated for routing synthesis. The antibody was successfully labeled with [18F]-N-succinimidyl 4-(fluoromethyl) benzoate in 50% to 70% yields in 10 minutes. The biodistribution study in rats showed that the labeled antibody was stable in vivo. Small amount of erytropoitin (about 20 microg) was labeled with [18F- N-succinimidyl 4-(fluoromethyl) benzoate. The specific activity of F- 18 labeled EPO was 1500-1800 Ci/mmol (EOS). The HCD57 cell binding assay showed specific binding of labeled EPO to EPO receptors. Both holo- and apo-transferrin were labeled with [18F]-N-succinimidyl 4-(fluoromethyl) benzoate. The specific activity of F-18 labeled transferrins was about 1000 Ci/mmol (EOS). The cell binding assay also showed binding of transferrin to transferrin receptors. Somatostatin is a 14 amino acid residue peptide with two lysine residues. The Somatostatin was labeled with [18F-N-succinimidyl 4- (fluoromethyl) benzoate to give two major isomers. These two isomers can be separated by HPLC. Since one of the lysines is essential for the receptor binding, one of the labeled can be used to study somatostin receptor binding and the other one used as the negative control for the study. A 15 oligomer of synthetic oligonucleotide with amino link attached to its 5' end was also used as the target for labeling. The study showed that this oligomer needs to be further purified to get better labeling yield.